Computed tomography and positioning of the anatomy desired to be imaged

ABSTRACT

The invention relates to a problem of setting mutual position of an anatomy being imaged and imaging means of a computed tomography imaging apparatus so that specifically the very volume of the anatomy desired to be imaged actually is imaged. To further the positioning, a positioning tool in a form of a three-dimensional virtual positioning model ( 40 ), generated from the anatomy to be imaged, is shown on a display from which the volume ( 41 ) of the anatomy desired to be imaged can be pointed, selected or defined.

FIELD OF INVENTION

The invention relates to positioning a volume to be imaged for computedtomography imaging or, to put it in other words, directing imaging to adesired anatomy. The invention particularly relates to the computedtomography imaging of the human or animal cranial area.

BACKGROUND OF INVENTION

Medical computed tomography imaging (CT imaging) is a form of X-rayimaging in which a volume to be imaged is irradiated from differentdirections and, from the data thus acquired, a desired two- orthree-dimensional image is reconstructed afterwards. When X-ray imaginga person, the imaging must be implemented by as small a radiation doseas possible to still enable diagnosis Due to this, one e.g. tries tokeep the size and shape of the volume to be imaged as small as possible.For example, it is typical for dental cone-beam computed tomography(CBCT) that it does not produce image information of an anatomy forreconstructing a cross section of volume of a width of a complete skullbut to reconstruct only a smaller partial volume, such as one covering aportion of a dental arch. Wishing to image a certain partial volume butsimultaneously trying not to image anything diagnostically inessentialnaturally causes a problem of positioning the anatomy being imaged tothe imaging apparatus such that specifically the desired volume of theanatomy can be imaged.

It is known to use in positioning of the anatomy e.g. variouspositioning lights, such as laser lines. Aligning such lights to adesired point in the anatomy always takes some time and, when the wholeprocess is based mostly on ‘educated guess’ on the position of thevolume desired to be imaged in relation to the external features of theanatomy, the positioning by even an experienced person can prove tohaving been inaccurate. In such cases, it is possible that the imagingmust be renewed, which increases the patient's total radiation dose andis in general frustrating and requires extra time from both the patientand the personnel.

It is also known to facilitate directing of the imaging by taking ascout X-ray image of the anatomy by a small radiation dose, from whichimage the location of the volume desired to get imaged can beidentified. However, the quality of such scout images is typically quitepoor and, on the other hand, even a small extra radiation dose does inany case always increase the radiation load.

BRIEF DESCRIPTION OF INVENTION

The object of the invention is to improve positioning of an anatomy forcomputed tomography imaging.

The invention as defined in the attached independent patent claims baseson a solution in which a virtual three-dimensional positioning model,being based on shapes of the surface of the anatomy being imaged, isshown on a display and utilized as a positioning tool. The volume of theanatomy desired to get imaged can be pointed, selected or defined fromthe positioning model. Some preferable embodiments of the invention arepresented in the attached dependent claims and described in more detailin the following.

The invention is thus based on a solution in which a patient ispositioned in the imaging area of a computed tomography imagingapparatus and a virtual positioning model generated of the patient beingimaged is shown on a computer display or a display arranged inconnection with the imaging apparatus. The positioning model can be e.g.a surface model generated based on optical imaging of the patient. Insuch a model, it is possible to point or select a volume desired to getimaged after which, information on the position of that volume istransmitted as control data to a control system of the computedtomography imaging apparatus. For the control system to know whichvolume in the set of coordinates of the imaging apparatus the volumeselected from the display corresponds to, the system also includesinformation on how the set of coordinates of the model shown on thedisplay is positioned in relation to the position of the X-ray imagemeans of the computed tomography imaging apparatus. One solution, forproviding this data is to produce information for generating the virtualpositioning model by optical means which are arranged as a part of thestructure of the computed tomography imaging apparatus, whereby thegeneration of the positioning model and the actual CT imaging can beperformed by the same apparatus and the same patient positioning.

The solution according to the invention provides a new kind of visualand easy-to-use possibility to direct the volume getting imaged at adesired place in the patient's anatomy and in a way which does notincrease radiation load. The display utilized in directing the imagingcan be placed in a separate space protected from radiation and thedirecting can be performed from there whereby, after the directing,there is no need to remain waiting for the person assisting the imagingto exit from the imaging set, for shelter from radiation.

BRIEF DESCRIPTION OF FIGURES

The invention is now described in more detail in reference to itspreferable embodiments and the attached drawings, of which:

FIG. 1 shows a typical apparatus used in cone-beam computed tomographyimaging;

FIGS. 2 and 3 show a first and a second example of a receiver module ofimage information suitable for use in the apparatus according to FIG. 1;

FIG. 4 shows a virtual positioning model and a positioning volume to beshown in connection with it; and

FIG. 5 shows one method according to the invention for positioning ananatomy for computed tomography imaging.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows a basic structure of one apparatus suitable for use incomputed tomography. The apparatus includes a vertical supportconstruction 11 from which horizontally extends an arm 12 supportingpatient support means and an arm part 13 which supports a structuresupporting imaging means of the apparatus, an arm part 14. In thestructure according to FIG. 1, the arm part 14 supporting the imagingmeans is arranged rotatable via a second rotatable arm part 14′, whichsolution offers versatile possibilities for moving the imaging means. Tothe arm part 14 supporting the imaging means are arranged at a distancefrom each other an X-ray source 15 and a receiver of X-ray imageinformation 21, which have been positioned to the apparatus with respectto a patient support means 17 such that to the apparatus is formed animaging station 18 located between the X-ray source 15 and the receiverof X-ray image information 21 such that a beam produced by the X-raysource 15 can be aligned to pass via the imaging station 18 towards thereceiver means of X-ray image information 21. The apparatus includes acontrol system of which FIG. 1 shows a control panel 16 arranged to thesupport construction 11 and an operating mode selection means 19pertaining in it. In the apparatus according to FIG. 1, the receivermeans of X-ray image information 21 are arranged as part of a receivermodule of image information 20, which is arranged in a functionalconnection with a computer 30 via e.g. a fixed or wireless connection,such as a cable, Bluetooth or wireless network. To the computer arearranged means for processing image information and means for showingimage information, which means include a display 31 for showing imagesgenerated by the computer.

FIG. 2 shows one receiver module of image information 20 applicable foruse in the apparatus according to FIG. 1. The module includes twooptical cameras 22 arranged horizontally on opposite sides of the X-raydetector 21 and aligned at the imaging station 18. Further, two lasers24 are arranged to the module 20, as well as light sources 23 preferablyproducing white light to illuminate the imaging station 18 and. Thelasers are positioned substantially in the middle of the module 20 tothe substantial proximity of its upper and lower edges. The lasers 24are arranged to emit and direct at the imaging station 18 a narrowvertical fan beam which casts a laser light pattern on the patient'sface.

The light sources 23 can be arranged to produce lights of other color orcolors than white. It is also possible to arrange to the apparatus morethan two or only one camera 22, and the cameras or camera 22 can bearranged to operate not only as a photographic camera but also as acontinuously-operating video camera. The light pattern to be cast on thepatient's face can be produced by some other light source than a laserand the color of this light pattern, too, can be arranged changeableand, when produced by a laser, its color can be some other than theconventional red, such as preferably particularly green.

A module of the type described above can be implemented by accommodatingonly a part of the above-mentioned components in it. As an example of adifferent module, FIG. 4 shows an arrangement which includes no lasers24 but which pertains cameras 22 on top of each other to form a camerapair on both edges of the module 20. Still, there can be cameras 22 ineither direction and even more than two.

FIG. 4 shows a virtual positioning model 40 of an anatomy and apositioning volume 41 shown in connection with it. The positioningvolume 41 shown in FIG. 4 is a cylinder but it may also be of some othershape. In a situation where a portion of the positioning volume 41 islocated outside and a portion inside the surface of the positioningmodel 40, it is possible to arrange the positioning volume 41 to bepresented looking different for these parts.

It is also possible to show at least two positioning models 40 whichshow the anatomy from different projection directions and, if in thatcase also the positioning volume 41 is shown, it is also possible toshow its location in relation to the positioning model 40 in eachprojection as seen from the corresponding direction.

FIG. 5 presents a method for directing computed tomography imaging to adesired volume of an anatomy being imaged. The method can utilize e.g.an arrangement shown in FIG. 1, which comprises a computed tomographyimaging apparatus including X-ray imaging means, a control system of thecomputed tomography imaging apparatus, and a means for showing imageinformation arranged in a functional connection with the computedtomography imaging apparatus. The computed tomography imaging apparatuscan be e.g. a computed tomography apparatus (CT) or a cone-beam computedtomography imaging apparatus (CBCT). The means for showing imageinformation can comprise e.g. a display 31, such as the display of acomputer, a phone or a tablet. The display can be e.g. a conventionalone or a touch screen.

In the method in step 300, an anatomy is positioned in the imaging areaof the imaging apparatus, e.g. in the case of the apparatus shown inFIG. 1, in the patient support means 17 of the imaging station 18. Themeans for showing image information, such as the display 31, shows instep 302 the virtual positioning model 40 generated of the anatomy beingimaged. The positioning model 40 can be e.g. a three-dimensional surfacemodel or a three-dimensional volume model which comprises at least aportion of a cranial anatomy. The positioning model 40 can also be atexture model. The positioning model 40 can be generated in advancebefore positioning the patient in the imaging area, whereby it can besaved e.g. in the computer memory and then be acquired from there uponimaging. On the other hand, if suitable means, such as a moduleaccording to FIG. 3 or 4, has been arranged to the computed tomographyapparatus, it is possible to generate the positioning model 40 when theanatomy to be imaged has been positioned in the imaging area of thecomputed tomography imaging apparatus. When in step 304 the location ofthe volume of the anatomy in the positioning model 40 desired to getimaged has been pointed, in step 306 the relation of the position of theset of coordinates of the positioning model 40 to the position of theX-ray imaging means of the computed tomography imaging apparatus isdetermined, whereby in step 308 one can transmit control data to thecontrol system of the computed tomography imaging apparatus for imagingthe desired volume of the anatomy. If the positioning model has beengenerated from image information acquired from the tomographic imagingapparatus in connection with a tomographic imaging event, the relationof the above-mentioned positions can be directly resolved from the knowngeometry of the components of the imaging apparatus and theircalibration data. Step 306 can be carried out in the process alreadyearlier than only after step 304. If the process utilizes a positioningmodel generated earlier or generated in some other way than from imageinformation acquired by the tomography apparatus itself, a calibrationarrangement is required for positioning the positioning model to theknown set of coordinates of the computed tomography imaging apparatus.

The positioning model 40 can thus be generated by an apparatus accordingto FIG. 1, for example, which comprises a module such as the oneaccording to FIG. 2 or 3, in which apparatus, the structure 14supporting the imaging means is arranged rotatable. Then, it is possibleto take pictures of an anatomy positioned at the imaging station 18 byan optical camera arrangement of the receiver module of imageinformation 20 from different directions and, in one possiblearrangement, of a laser or some other light pattern projected on theanatomy. When using e.g. the arrangement according to FIG. 2, in whichthe cameras 22 and the lasers 24 are positioned at a distance from eachother, it is possible to scan with the laser line the anatomy positionedat the imaging station 18 and, at the same time, take pictures of theanatomy at an angle with respect to the direction of the laser beam.From thus acquired image information, it is possible to generate athree-dimensional surface model to be used as the positioning model 40,which can be shown on the display 31.

The volume desired to get imaged can be pointed in the positioning model40 e.g. by means of a computer mouse, a keyboard and/or by pointing thedesired point directly on the display 31. It is possible to facilitatethe pointing by showing on the display 31 a positioning volume 41 whichcan be moved. By means of the position volume, the location of thevolume desired to get imaged in the positioning model 40 can be pointedor determined. The positioning volume 41 can be of the shape of e.g. acylinder and correspond by its dimensions the volume the imagingapparatus is arranged to image. In one embodiment, the dimensions of thepositioning volume 41 can be changed, which change is then communicatedto the control system of the imaging apparatus.

To sum up, the method according to the invention for positioning ananatomy for computed tomography imaging can be described as a method inwhich an arrangement is used which comprises a computed tomographyimaging apparatus including X-ray imaging means, a control system of thecomputed tomography imaging, apparatus and a means for showing imageinformation arranged in a functional connection with the computedtomography imaging apparatus. In the method, an anatomy including avolume desired to get imaged is positioned in the imaging area of thecomputed tomography imaging apparatus and a virtual positioning model isshown by the means for showing image information, the positioning modelshowing at least a portion of a three-dimensional surface of the anatomyand comprising the volume desired to get imaged. The location of thevolume desired to get imaged is pointed, selected or determined in thevirtual positioning model and, when the relation of a position of a setof coordinates of the virtual positioning model to a position of a setof coordinates of the X-ray imaging means of the computed tomographyimaging apparatus has been resolved, control information is transmittedto the control system of the computed tomography imaging apparatus forimaging the volume of the anatomy desired to get imaged—which controlinformation is thus based on the knowledge of the relation of theposition of the set of coordinates of the virtual positioning model tothe position of the set of coordinates of the X-ray imaging means of thecomputed tomography imaging apparatus and knowledge of the location inthe positioning model of the volume desired to get imaged.

To facilitate the method, the means for showing image information canshow a positioning volume, such as a volume comprising a cylindersurface, by means of which the location of the volume in the virtualpositioning model desired to get imaged can be pointed, selected ordetermined. The dimensions of the positioning volume can be determinedin advance or they can also be changeable. At least one of actions i)moving the anatomy in the imaging area, ii) moving the volume desired toget imaged shown on the means for showing image information, iii) movingthe X-ray imaging means, may be included in the pointing, selecting ordetermining the position of the volume to get imaged. E.g. in a case inwhich the imaging apparatus according to FIG. 1 is utilized, in whichthe position of the rotation axis of the arm part 14 supporting theimaging means is freely adjustable within its operational range, theretypically is no need for moving either the anatomy or the imaging meansbefore the imaging but the imaging can be implemented starting from anoriginal positioning but then implementing the actual imaging—i.e. themotions during the imaging—in accordance with the determination made onthe display by means of the positioning model 40, whereby specificallythe desired anatomy can be imaged.

When the anatomy has been positioned in the imaging area of the computedtomography imaging apparatus, the positioning model can be generated inreal-time and it can also be updated while the anatomy being imaged ispositioned in the imaging area of the computed tomography imagingapparatus. Hence, e.g. by utilizing an optical camera arrangement, it ispossible to use the relation of the set of coordinates of thepositioning model to the position of the imaging means of the computedtomography imaging apparatus to identify the position of the patient inthe imaging area during computed tomography imaging and, if the positionof the anatomy is noticed to change, the motion of the X-ray imagingmeans during the imaging is controlled by correcting their motion in away corresponding the change in the position of the patient i.e. tocompensate for the change occurred in the patient's position.

The positioning model can thus be a model based on optical information,and information for the generating thereof can be produced by an opticalcamera arrangement arranged in the computed tomography imagingapparatus. The camera arrangement can be moved with respect to theanatomy being imaged in at least first motion direction and it cancomprise i) a camera arrangement in which at least two optical camerasare positioned at a distance from each other in said motion direction orii) at least two camera arrangements according to structure i)positioned at a distance from each other, in a substantiallyperpendicular direction with respect to said motion direction.

The method can be preferably applied in connection with imaging acranial area, such as portions of the dental arch, whereby the virtualpositioning model comprises at least a portion of the patient's cranialanatomy.

The positioning model can also be generated in advance beforepositioning the anatomy in the imaging area of the computed tomographyimaging apparatus for computed tomography imaging, whereby the positionof its set of coordinates in relation to the position of the set ofcoordinates of the X-ray imaging means of the computed tomographyimaging apparatus can be made to correspond the position of the anatomypositioned in the imaging area of the computed tomography imagingapparatus in relation to the position of the set of coordinates of theX-ray imaging means of the computed tomography imaging apparatus.

The computed tomography imaging apparatus again can be described ascomprising an x-ray imaging means which includes an X-ray source and areceiver means of image information, an imaging station, a controlsystem, a means arranged in a functional connection with the computedtomography imaging apparatus for processing image information as well asa means for showing image information. The control system of such anapparatus comprises:

a means for showing on said means for showing image information avirtual positioning model, the positioning model showing at least aportion of a three-dimensional surface of an anatomy being imaged andcomprising a volume desired to get imaged from said anatomy,

a means for pointing, selecting or determining a position of the volumedesired to get imaged in said virtual positioning model,

a means for determining the relation of a position of a set ofcoordinates of said virtual positioning model to a position of a set ofcoordinates of the imaging means of the computed tomography imagingapparatus, and

a means for transmitting to the control system of the computedtomography imaging apparatus control information for imaging said volumeof the anatomy desired to get imaged, which control information is basedon knowledge of the relation of the position of the set of coordinatesof said virtual positioning model to the position of the set ofcoordinates of the X-ray imaging means of the computed tomographyimaging apparatus and knowledge of the position of said volume desiredto get imaged in said virtual positioning model.

Preferably, the control system of the apparatus comprises a means forshowing on said means for showing image information a positioning volumeby means of which the location of the volume in said position modeldesired to get imaged is pointed, selected or determined.

Furthermore, the control system may comprise a means for adjusting atleast one of the following: the position of the positioning volume, oneor more dimensions of the positioning volume, the position of the X-rayimaging means.

The apparatus can also comprise an optical camera arrangement and itscontrol system a means for generating the positioning model frominformation produced by said optical camera arrangement. Such a cameraarrangement can comprise e.g. i) a camera arrangement in which at leasttwo optical cameras are positioned at a distance from each other in afirst direction or ii) at least two camera arrangements according tostructure 1) positioned at a distance from each other in a substantiallyperpendicular direction with respect to said first direction.

Various features of the invention may have been described above in partin a more general terms or as a part of an imaging process while it isclear that features of the invention the implementation of which relatesto structures or functions of an imaging apparatus, such as functionsimplemented according to a configuration of a control system, pertain inthe features of an imaging apparatus according to the invention.

It is obvious for those skilled in the art that when technologyadvances, the basic idea of the invention may be implemented in manydifferent ways. The invention and its embodiments are thus not limitedby the examples described above but they may vary within the scope ofthe patent claims.

1-20. (canceled)
 21. A method for positioning an anatomy for imaging, inwhich method, an arrangement is used which comprises imaging apparatusincluding X-ray imaging means, a control system of the imaging apparatusand a means for showing image information arranged in a functionalconnection with the imaging apparatus, in which method an anatomyincluding a volume desired to get imaged is positioned in the imagingarea of the imaging apparatus, a virtual positioning model is shown bysaid means for showing image information, the positioning model showingat least a portion of a three dimensional surface of said anatomy andcomprising the volume desired to get imaged, a location of the volume insaid virtual positioning model desired to get imaged is pointed,selected or determined, a relation of a position of a set of coordinatesof said virtual positioning model to a position of a set of coordinatesof the X-ray imaging means of the imaging apparatus is resolved, controlinformation is transmitted to the control system of the imagingapparatus for imaging said volume of the anatomy desired to get imaged,which control information is based on knowledge of the relation of theposition of the set of coordinates of said virtual positioning model tothe position of the set of coordinates of the X-ray imaging means of theimaging apparatus and knowledge of the location in said virtualpositioning model of said volume desired to get imaged.
 22. A methodaccording to claim 21, wherein said means for showing image informationalso shows a positioning volume, by means of which the location of saidvolume in said position model desired to get imaged is pointed, selectedor determined.
 23. A method according to claim 22, wherein saidpositioning model comprises a cylinder surface.
 24. A method accordingto claim 22, wherein when a part of the positioning volume is locatedoutside the surface of the positioning model and a part inside thesurface of the positioning model, for those parts, the positioningvolume is presented looking different.
 25. A method according to claim21, wherein at least two positioning models are shown which show saidanatomy from different projection directions, whereby in the case ofalso the positioning volume is shown, also its position in relation tothe positioning model can be shown in connection with each positioningmodel as seen from the corresponding direction.
 26. A method accordingto claim 22, wherein the dimensions of said positioning volume aredetermined in advance and/or are changeable.
 27. A method according toclaim 21, wherein the pointing, selecting or determining of the locationof said volume desired to get imaged comprises at least one of actionsi) moving the anatomy in said imaging area, ii) moving the volumedesired to get imaged shown on said means for showing image information,iii) moving the X-ray imaging means.
 28. A method according to claim 21,wherein said virtual positioning model is a surface model or whereinsaid virtual positioning model is a volume model.
 29. A method accordingto claim 21, wherein said virtual positioning model is a model based onoptical information.
 30. A method according to claim 29, whereininformation for generating said virtual positioning model is produced byan optical camera arrangement arranged to the imaging apparatus.
 31. Amethod according to claim 30, wherein information for generating saidvirtual positioning model is produced by an arrangement which is movedwith respect to the anatomy being imaged in at least first motiondirection and which comprises i) a camera arrangement in which at leasttwo optical cameras are positioned at a distance from each other in saidmotion direction or ii) at least two camera arrangements according tostructure i) positioned at a distance from each other in a substantiallyperpendicular direction with respect to said motion direction.
 32. Amethod according to claim 30, wherein said optical camera arrangementand said relation of the set of coordinates of the virtual positioningmodel to the position of the imaging means of the imaging apparatus areutilized for identifying the position of the patient in the imaging areaduring imaging and, if the position of the anatomy is noticed to change,the motion of said X-ray imaging means is controlled during the imagingto compensate for the change in the position of the patient.
 33. Amethod according to claim 21, wherein said virtual positioning modelcomprises at least a portion of a patient's cranial anatomy.
 34. Amethod according to claim 21, wherein said virtual positioning model isgenerated in advance before positioning the anatomy in the imaging areaof the computed tomography imaging apparatus for computed tomographyimaging and wherein the relation of the position of the set ofcoordinates of the positioning model to the position of the set ofcoordinates of the X-ray imaging means of the computed tomographyimaging apparatus is made to correspond the position of the anatomypositioned in the imaging area of the computed tomography imagingapparatus in relation to the position of the set of coordinates of theX-ray imaging means of the computed tomography imaging apparatus.
 35. Acomputed tomography imaging apparatus which comprises an X-ray imagingmeans which includes an X-ray source and a receiver means of imageinformation, an imaging station, a control system, a means arranged in afunctional connection with the computed tomography imaging apparatus forprocessing image information as well as a means for showing imageinformation, in which apparatus, the control system comprises: a meansfor showing on said means for showing image information a virtualpositioning model, the virtual positioning model showing at least aportion of a three-dimensional surface of an anatomy being imaged andcomprising a volume desired to get imaged from said anatomy and beinggenerated in real-time when the anatomy has been positioned in saidimaging area of the computed tomography imaging apparatus and/or updatedin real-time while the anatomy being imaged is positioned in saidimaging area of the computed tomography imaging apparatus, a means forpointing, selecting or determining a location of the volume in saidvirtual positioning model desired to get imaged, a means for determininga relation of a position of a set of coordinates of said virtualpositioning model to a position of a set of coordinates of the imagingmeans of the computed tomography imaging apparatus, and a means fortransmitting control information to the control system of the computedtomography imaging apparatus for imaging said volume of the anatomydesired to get imaged, which control information is based on knowledgeof the relation of the position of the set of coordinates of saidvirtual positioning model to the position of the set of coordinates ofthe X-ray imaging means of the computed tomography imaging apparatus andknowledge of the location of said volume in said virtual positioningmodel desired to get imaged.
 36. An apparatus according to claim 35,wherein said control system comprises a means for showing on said meansfor showing image information a positioning volume, by means of whichthe location of said volume in said position model desired to get imagedis pointed, selected or determined.
 37. An apparatus according to claim35, wherein said control system comprises a means for adjusting at leastone of the following: the position of said positioning volume; one ormore dimensions of said positioning volume; the position of said X-rayimaging means.
 38. An apparatus according to claim 35, which comprisesan optical camera arrangement and said control system comprises a meansfor generating said positioning model from information produced by saidoptical camera arrangement.
 39. An apparatus according to claim 38,wherein said camera arrangement comprises i) a camera arrangement inwhich at least two optical cameras are positioned at a distance fromeach other in a first direction or ii) at least two camera arrangementsaccording to structure i) positioned at a distance from each other in asubstantially perpendicular direction with respect to said firstdirection.
 40. A computed tomography imaging apparatus comprising anX-ray imaging device including an X-ray source and a receiver, animaging station, a control system, a processor, a camera, and a display;the processor configured to show on said display a three-dimensionalsurface of an anatomy being imaged as received from the camera; thecontrol system configured for pointing, selecting or determining alocation of a volume desired to get imaged based on thethree-dimensional surface of an anatomy shown on the display; and theprocessor configured to correlate a position of the location of a volumedesired to get imaged to a position of the imaging apparatus.